/**
 * Using Thread
 * @param imageView
 * @param url
 */
public void showImageByThread(final ImageView imageView, final String url) {

    mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Bitmap bitmap = (Bitmap) msg.obj;
            imageView.setImageBitmap(bitmap);
        }
    };
    new Thread() {
        @Override
        public void run() {
            Bitmap bitmap = getBitmapFromUrl(url);
            Message message = Message.obtain();
            message.obj = bitmap;
            mHandler.sendMessage(message);
        }
    }.start();
}

public View getView(int position, View convertView, ViewGroup parent)

当它再显示的时候，又一次再写上正确的数据就好了。

可是异步就不一样了，就拿我们这里下载图片来说，每一个图片都有自己的脾气。大家下载的速度都是不一样的，当初始显示ListView时。Item1的图片下载太慢，当你滑上去，显示Item11了，Item11的图显示的飞起，立即就下好了。OK，Item11的图显示好了，可立即。Item1下的慢的图也下好了，它去找Item1，可是它不知道这个时候的Item1已经变成Item11了。它还去给人家设置图像。这不就乱了吗？

所以，我们须要建立一个标志，来让冬眠的朋友回来看看清楚，如今的这个大爷是不是你曾经的那个大爷。

/**
 * Using Thread
 * @param imageView
 * @param url
 */
public void showImageByThread(final ImageView imageView, final String url) {

    mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            ImgHolder holder = (ImgHolder) msg.obj;
            if (holder.imageView.getTag().equals(holder.url)) {
                holder.imageView.setImageBitmap(holder.bitmap);
            }
        }
    };
    new Thread() {
        @Override
        public void run() {
            Bitmap bitmap = getBitmapFromUrl(url);
            Message message = Message.obtain();
            message.obj = new ImgHolder(imageView, bitmap, url);
            mHandler.sendMessage(message);
        }
    }.start();
}

private class ImgHolder {
    public Bitmap bitmap;
    public ImageView imageView;
    public String url;

    public ImgHolder(ImageView iv, Bitmap bm,String url) {
        this.imageView = iv;
        this.bitmap = bm;
        this.url = url;
    }
}

这里就利用到了我们在Android异步载入全解析之开篇瞎扯淡里面所提到的：

viewHolder.imageView.setTag(url);

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    String url = mData.get(position);
    ViewHolder viewHolder = null;
    if (convertView == null) {
        viewHolder = new ViewHolder();
        convertView = mInflater.inflate(R.layout.listview_item, null);
        viewHolder.imageView = (ImageView) convertView.findViewById(R.id.iv_lv_item);
        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
    }
    viewHolder.imageView.setTag(url);
    viewHolder.imageView.setImageResource(R.drawable.ic_launcher);
    mImageLoader.showImageByThread(viewHolder.imageView, url);
    return convertView;
}

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